Tolerance rings constrain movement between relatively moving parts, such as rotating shafts in housing bores. One type of tolerance ring is an annular band located in the gap between the outer surface of the shaft and the inner surface of the bore. This tolerance ring limits radial motion of the shaft within the bore while still permitting rotation.
In conventional tolerance ring configurations, a close fit between the inner and outer components is sought. In addition, either forces for providing maximal frictional engagement or minimal variation in sliding forces are sought. A close fit between the components is desirable because it reduces relative vibration between the parts. These requirements between the inner and outer components require strong and substantial contact, which increases frictional forces.
Tolerance rings that provide torque overload protection for applications with torques greater than 50 Nm, with relatively low rates of rotation and small angular slip cycles also are known. These applications include reduction gear mounts, power steps on four wheel drive trucks and seat motors for fold away seats. Tolerance rings for these applications tend to be heat-treated carbon steel, greater than 0.40 mm thick, and have many strong, high friction waves to provide the required torque. Although these solutions are workable for some applications, improvements in tolerance rings continue to be of interest.